5. Pathways to Decarbonization of Energy

History of industrial civilization is history of the progression of primary fuel substitution: wood → coal → oil → gas. This evolutionary trend of reducing carbon intensity of primary energy is referred to as decarbonization. During these historical transitions, human society moved to more convenient, efficient, and clean energy sources that enabled new technological advances in industry, transportation, and other areas. However, during the last couple of decades, this positive decarbonizing trend dramatically slowed down and practically ceased. In this chapter, the current trends in carbon intensity of global economy and prospective decarbonization options are analyzed using Kaya Identity (KI) modeling tool. The KI analysis indicates that the cessation of decarbonization of global economy can be largely attributed to a reversal of the evolutionary fuel substitution trend and “detour” to coal by populous rapidly developing countries. Dramatic reductions in both energy and carbon intensities of world economy would be necessary to stop and reverse this worrisome trend. Among proposed carbon mitigation policies, improvements in energy efficiency promise the largest near-term dividends and are central to achieving atmospheric CO₂ stabilization goals.